This invention relates to blends of carbonate polymers with rubber-modified monovinylidene aromatic polymers.
Carbonate polymers derived from reactions of dihydroxyorganic compounds, particularly the dihydric phenols, and carbonic acid derivatives such as phosgene have found extensive commercial application because of their excellent physical properties. These thermoplastic polymers appear suitable for the manufacture of molded parts wherein impact strength, rigidity, toughness, heat resistance, excellent electrical properties, glass-like transparency and good clarity are required.
Unfortunately, however, these polymers are expensive in price and require a high amount of energy expenditure in extrusion and molding processes. In order to reduce the cost of processing carbonate polymers, said polymers may contain additives that reduce costs and lower the temperatures required for molding processes. The blends resulting from the processing of carbonate polymer and additive generally exhibit improved melt flow properties at the sacrifice of other desirable features such as heat resistance, impact strength, and the like. In addition, blends of carbonate polymer and additive often exhibit an undesirable, glossy finish.
Another disadvantage of carbonate polymers is that such polymers exhibit low temperature impact strengths which are severely reduced from those impact strengths which are exhibited at room temperature (i.e., about 20.degree. to about 25.degree. C.). Such poor low temperature properties of such polymers severely limit the use of said polymers in exterior applications when articles prepared from said polymers are exposed to great fluctuations in temperature, especially at low temperatures. Blends of carbonate polymer and additive generally do not exhibit to any significant extent improved low temperature impact strengths of the carbonate polymer.
In view of the deficiencies of the conventional carbonate polymers and blends thereof, it would be highly desirable to provide an economical carbonate polymer composition which exhibits exceedingly high low temperature impact strength and improved processability while retaining, to some degree, the desirable properties characteristic of carbonate polymers such as room temperature impact strength and heat resistance, and which is additionally capable of exhibiting a very low gloss finish.